I just installed the Adblock Plus extension for Firefox - it's an amazingly smart ad filtering add-on that eliminates all ads (so far). You can train it like a spam filter or use a pre-existing "subscription" (it's just a term - it costs nothing) that has been tailored for your language/region. For example, I chose the Easylist USA subscription and it's working great. Go to Myspace, CNN.com, (the Noiseboard!), whatever - and the ads are just gone.
Now, there's an ethical debate that will develop... Basically, this is like a mega-Tivo (in that ads can be skipped) that is able subvert the very economic engine that the Internet runs on - ad revenue. This could mean that (A) advertisers will have to come up with more creative (and possibly insidious) ways to reach eyeballs, and (B) ad revenue will fall for sites, causing them to limit their "free" services.
Then again, ads are fucking annoying - especially the ones that make noises or run video that eats up bandwidth. As for now, there probably won't be a significant impact from some people using a service like this because hits are still being counted on the site, and those hits will still dictate how much advertisers are charged. Soon, however, advertisers will notice that yes, the site is being hit, but less and less people are clicking on the ads (which are now invisible) and they're not being redirected to the advertiser's site. If enough people used effective ad-blocking software like this, advertisers could see a serious decline in sales.